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Introduction

Description:Projected changes in climate (temperature and precipitation means and extreme events), increased atmospheric carbon dioxide (CO 2 ), and increased nitrogen deposition are likely to affect U.S. forests throughout this century. Effects will be both direct (e.g., effects of elevated CO 2 on forest growth and water use) and indirect (e.g., altered disturbance regimes), and will differ temporally and spatially across the United States. Some of these effects may already be occurring. For example, large insect outbreaks and large wildfires during the past decade (Bentz et al. 2009, Turetsky et al. 2010) are a wake-up call about the potential effects of a rapidly changing climate on forest ecosystems. Individually and in combination, these two major disturbance phenomena are reshaping some forest landscapes and may be causing longterm, possibly permanent changes in forest structure, function, and species composition (Hicke et al. 2012, McKenzie et al. 2004). Combined with other stressors, such as invasive species and air pollution (McKenzie et al. 2009), and a legacy of fire exclusion and other land management activities, maintaining resilience and restoring forest ecosystems in the face of climate change will be a major challenge for the 21 st century and beyond (Peterson et al. 2011).